Electric circuit interrupter



Feb. 18 1936. c THUNHN ELECTRIC CIRCUIT INTERRUPTER Filed July 5, 1954 lnventorr Carl Thurnirn,

is torney Patented Feb. 18, 1936 UNITED STATES 2,031,51 ELsc'raIccmcUIr ru'rsaaor'rsa Carl Thumim, Philadelphia, Pa.,

assignor to General Electric Company, a. corporation of New York Application July 3, 1934 Serial No. 133,563

2 Claims.

My invention relates to electric circuit interrupters and has for its principal object the provision of an improved circuit interrupter in which burning" of the contacts during interruption of heavy currents is minimized and which has increased interrup'ting'capacity and comparatively high operating speed.

The interruption of high tension power circuits by oil circuit breakers, for example, is often attended 'by excessive burning of the contact material which is usually copper. The burning or melting away of the contact material by heavy arcs may after a number of operations necessitate taking the breaker temporarily out 01- service and installing new contact structure. Furthermore, in order to compensate for burning comparatively large masses of contact material are used, thereby increasing the inertia of the moving parts and the cost of the breaker.

In accordance with my invention, burning is greatly minimized by means of a substantially non-inductive resistance which is inserted in series in the circuit to be interrupted upon separation of the main current-carrying contacts, and the circuit breaker structure is simplified and adapted for high speed operation by incorporating said resistance in the stationary contact assembly.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is a diagrammatic illustration of a circuit interrupter embodying my invention, and Fig. 2 is an elevational view, partly in section, of coacting contact structure of one pole of an oil circuit breaker embodying my invention.

There is diagrammatically illustrated in Fig. 1 a circuit interrupter comprising a pair of fixed contacts I and 2 adapted to be interconnected by a movable conducting bridging member 3 in the closed circuit position. The stationary contacts are connected in the circuit to be interrupted by conductors 4 and 5, respectively. For the purpose of minimizing burning of the contact material when the bridging member 3 is lowered during the circuit opening operation, each pole of the circuit interrupter is provided with a pair of substantially non-inductive resistances 6 and 1 suitably connected between a main circuit conductor, as 5, and an auxiliary fixed contact 8. In the present instance the resistances 6 and 1 are shown as connected in parallel with each other, it being understood, of course, that the amount of resistance may be'varied in accordance with the interrupting requirements of the circuit breaker. The auxiliary contact 8 is adapted to coact in sliding engagement with the contact 9 electrically connected to' and carried by the bridging member 3. The contacts 8 are likewise adapted to engage the stationary contacts when the bridging member is elevated for completing the circuit.

The contacts 9 may likewise engage the contacts 8 in the closed circuit position, the aforesaid contacts being in sliding engagement during the initial circuit'opening movement and after separation of the stationary contacts and bridging member. In the position illustrated the bridging member 3 may be considered as moving downwards to the open circuit position, the main current-carrying contacts having separated and the resistances 6 and I now being in series in the circuit through the contacts 8 and 9. Upon separation of the main current-carrying contacts little or no arcing 'will take place as the circuit is not open, the'current, on the other hand, being materially decreased by the insertion of resistances above described. Accordingly, upon final separation of the contacts 8 and 9 the current has been appreciably reduced so that interruption of the circuit is not only more easily eii'ected but is accompanied by much lower intensity.

It will likewise be apparent that burning of the contact material due to closing of the circuit interrupter on. heavy load currents is also minimized in view of the fact that the contacts 8 and 9 are the first to engage. The resistance so inserted decreases the current to such an extent that subsequent closing of the main current-carrying contacts is not accompanied by burning.

Referring more particularly to Fig. 2 which illustrates the detailed structure of one pole of the circuit interrupter diagrammatically illustrated by Fig. 1, the stationary contact structure 2 comprises a contact adapter ID of conducting material which is electrically connected tothe lower end of the circuit conductor stud 5 and which carries at its lower end finger contacts ll arranged to be engaged by the movable bridging member 3. The finger contacts H may be of any suitable and well known type and are arranged in pairs so as to be engaged and spread apart by the wedge-shaped contact portion 9 of the bridging member.

For the purpose of simplifying the stationary ed'within the aperture l2.

contact assembly, the adapter I is provided with aperture or bores I2 extending therethrough in which the resistance elements 6 and 1 are disposed. Each resistance element or unit may comprise a resistance wire l3 wound on a cylinder M of insulating material, one terminal of each unit, as 6, being electrically connected as at I5 to a conducting plate l6 secured tothe adapter and closing one end of each aperture I2, and. the other terminal being connected as at I! to conducting strips l8. Each resistance element, except for terminal 15, is insulated with respect to the adapter ID by any suitable means as the concentric insulating cylinders I9 which are mount- The terminal conducting strips l8 are mounted on an insulating plate 20 which is in turn secured, as at 2|, to the adapter. The insulating plate 20 is provided with apertures 22 in alinement with apertures [2 for receiving one end of each resistance element.

The conducting strips l8 terminate in the auxiliary contact 8 which is engaged by the coacting auxiliary member 9 of the bridging contact portion 9 during a part of the travel of the bridging member. The auxiliary contact 8 is not only electrically connected to the resistance elements through the conducting strips l8 but is biased into resilient contact engagement with member ,9 thereby.

Accordingly, upon either circuit opening or circuit closing movement the bridging member 3 when in the lower dotted line position shown is connected with the auxiliary contacts 8 so that vvthe resistances B and l are connected in series in the circuit to be interrupted, resulting in improved operation which prolongs greatly the operating life of the portions of the contact structures 9 and H and in addition increases the interrupting capacity of the circuit interrupter by reason of the fact that arcing is more readily extinguished. The operating speed of the breaker is likewise comparatively high since the mass oflthe moving elements may be reduced by the amount of copper generally lost by burning, the additional structure associated with my invention being incorporated in the stationary contact assembly.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

1. An electric circuit interrupter comprising coacting stationary and movable contact structure, said stationary structure including a lead-in conductor, a block of conducting material forming an adapter connected to said lead-in conductor, main and auxiliary contacts supported by said block, and a resistance coil positioned in a recess formed in said block, one terminal of said coil electrically connected to said block and the other terminal electrically connected to said auxiliary contact, said movable contact structure likewise including main and auxiliary contacts for coacting respectively with the aforesaid stationary main and auxiliary contacts.

2. An electric circuit interrupter comprising coacting stationary and movable contact structure, said stationary structure including a lead-in conductor, a block of conducting material forming an adapter connected to said lead-in conductor, main contacts supported by and electrically connected to said block, a'resistance coil positioned in a bore extending transversely through said block, a plate of conducting material secured to said block for closing one end of said bore, one

terminal of said coil electrically connected to said 1 plate, a plate of insulating material secured to said block closing the other end of said 'bore,'an auxiliary contact mounted on said insulating plate and electrically connected to the other ter- 4 minal of said coil, said movable contact structure including main and auxiliary contacts for coacting respectively with said stationary main and auxiliary contacts.

CARL THUMIM. 

